The 600 comet I did recently, we gave it 0.006" after we installed a new liner and rings, as over size pistons are not readily available. It is also worth noting on the top end kits supplied from Terry that the liner should be lapped into the head recess, even if the liner/muff has been assembled, and although you cannot rotate it much you still can enough to work. The tooling marks from where the CNC machine has cut out the liner recess in the head leaves an overlapping area that can and will leak over time. I still go to the trouble of running the oil feed to the rear of the skirt on all engines I do, as it cannot do any harm, even if you use a restrictor disc in the timing cover just on the cylinder feeds. On big bore engines, just dremel the oil feed gallery back around the case mouth to center it at the rear again.